Sweep waveform is also called sawtooth or ramp function wave forms. Its is extensively used as a time-base in oscilloscopes, radar indicators, computer monitors etc.

A sawtooth wave form has a rise time and a fall time.Rise time is much longer than fall time.the sawtooth wave form can be generated by charging and discharging a capacitor with proper RC time constant.

In the absence of the input signal or when the input signal is at negative level, transistor is in off state because there is no base emitter bias.then capacitor C charges through Rc towards the Vcc supply.When the positive pulse appears at the input, transistor turns ON and capacitor discharges through transistor to ground.If time-constant Rcc is large compared to the time period of sawtooth waveform , C will charge to only a part of the way toward Vcc.